Infant mortality and Mortality rate

Infant mortality noun - The death rate during the first year of life.

Mortality rate and infant mortality are semantically related. In some cases you can use "Mortality rate" instead a noun phrase "Infant mortality".

Mortality rate noun - The ratio of deaths in an area to the population of that area; expressed per 1000 per year.

Infant mortality and mortality rate are semantically related. Sometimes you can replace phrase "Infant mortality" with "Mortality rate", this phrases are similar.